The present invention relates in general to a corona charger for use in an electrostatographic reproduction apparatus or the like, and more particularly to an automatic cleaning mechanism for the corona wires and grid of a corona charger.
In typical commercial electrostatographic reproduction apparatus (such as copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member, and an electric field applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric member and the image is fixed to the receiver member by heat and/or pressure to form a permanent reproduction thereon.
The electrostatic fields for various reproduction apparatus operations are commonly provided by corona charging devices. For example, corona chargers may be used to deposit the uniform charge on the dielectric member prior to forming the latent image charge pattern, to implement transfer of a developed image from the dielectric member to a receiver member, or to neutralize charge on the dielectric member subsequent to developed image transfer to facilitate release of the receiver member or residual marking particles from the dielectric member.
Corona chargers typically include at least one very thin corona wire, located within a housing shell. The corona wire is electrically coupled to a high voltage potential source to generate ions or charging current to charge a surface (such as the dielectric member surface) brought into close proximity with the corona wire. The corona wire is tightly suspended between insulating end blocks, supported in the housing shell, such end blocks being connected to a high voltage source for producing the ion generating condition around the corona wire. A grid may be located between the corona wire and the surface to be charged. The grid is held at a preselected electrical potential to control the specific charge to be laid down on the surface.
It should be well appreciated that the high voltage of the corona wire creates a corrosive environment which adversely affects the wire. That is, the electrically charged atmosphere surrounding the wire is conducive to the promotion of coating and/or pitting of the wire by airborne marking particles, fuser oil mist, or paper dust. Over time, such action on the corona wire will cause the wire, which by its very nature is extremely fragile, to no longer be effective in producing the desired uniform charging of the surface intended to have a charge applied thereto. That is, irregularities in the corona wires will cause charging irregularities which show up as defects in the reproduction being formed. The defects may typically include streaks, spots or mottle. Accordingly, the corona charger, and particularly its grid and corona wires, has to be periodically cleaned to assure proper operation and prolong its useful life.
Examples of corona charger cleaners are shown for example in U.S. Pat. Nos. 3,870,883 (issued Mar. 11, 1975, in the name of Oagley), and, 4,864,363 (issued Sep. 5, 1989, in the name of Shinada). These patents show corona wire cleaners. However, they do not provide for cleaning of the corona charger grid. As such, even though the corona wires are cleaned, the overall effectiveness of the chargers is substantially degraded since the uncleaned grids interfere with the proper corona charger performance. Another example of a corona charger cleaner is found in the Ektaprint EK 85, available from Eastman Kodak Company of Rochester, N.Y. This corona charger cleaner does provide for cleaning of the grid as well as the corona wires. However, the structure is complex, and only provides for cleaning of the surfaces of the corona wires facing in the direction parallel to the surface to be charged. Since the surfaces of the corona wires facing perpendicular to the surface being charged are the primary surfaces from which ions are discharged to the surface being charged, the failure to clean such surfaces represents a severe shortcoming of such cleaner.